你执行了如下命令： a.grant select on hr.regions to jon; b.grant all on hr.regions to jon; c.grant dba to jon; d.grant select on hr.regions to public; 哪些授权应该回收来避免JON看见HR.REGIONS的内容？ACD A a, c, and d B a, b, and c C b, c, and d D a, b, c, and d E c and d